dna – october 5, 2010 1.what do we mean when we talk about the trophic structure of a community?...

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DNA – October 5, 2010 1.What do we mean when we talk about the trophic structure of a community? 2.What’s the difference between an autotroph and a heterotroph? 3.What is ALWAYS going to be at the top of the food chain/food web? Why? 4.Why is there a limit to the # of links in a food chain?

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Page 1: DNA – October 5, 2010 1.What do we mean when we talk about the trophic structure of a community? 2.What’s the difference between an autotroph and a heterotroph?

DNA – October 5, 2010

1. What do we mean when we talk about the trophic structure of a community?

2. What’s the difference between an autotroph and a heterotroph?

3. What is ALWAYS going to be at the top of the food chain/food web? Why?

4. Why is there a limit to the # of links in a food chain?

Page 2: DNA – October 5, 2010 1.What do we mean when we talk about the trophic structure of a community? 2.What’s the difference between an autotroph and a heterotroph?

Influential Species in Communities

Ms. KlinkhachornOctober 5, 2010

AP Biology

Page 3: DNA – October 5, 2010 1.What do we mean when we talk about the trophic structure of a community? 2.What’s the difference between an autotroph and a heterotroph?

Dominant Species

• Most abundant species in a community– Community: 50A, 10B, 5C, 5D, 15, E, 15F

• Have a lot of control over the distribution of other species– Example: If a maple tree is your dominant species,

it affects abiotic factors like shade and soil nutrients. This shade and soil composition affect the other species that can grow there

Page 4: DNA – October 5, 2010 1.What do we mean when we talk about the trophic structure of a community? 2.What’s the difference between an autotroph and a heterotroph?

Why do species become dominant?

• Have a competitive advantage• Good at avoiding predation or disease– Example: invasive species (not native)

• Think about what happens when you remove a dominant species from a community

Page 5: DNA – October 5, 2010 1.What do we mean when we talk about the trophic structure of a community? 2.What’s the difference between an autotroph and a heterotroph?

Keystone Species

• Don’t have to have a high abundance, but have a strong control because of their niches– Removal of a keystone species would affect the

species richness of an area

Page 6: DNA – October 5, 2010 1.What do we mean when we talk about the trophic structure of a community? 2.What’s the difference between an autotroph and a heterotroph?

Foundation Species (Engineers)• These species physically

change the environment– Example: Beaver

• Also called facilitators because they have positive effects on other species– Example:

• Black-needle rush (a plant)

• Prairie Dog